Nowadays, a variety of cooking utensils such as gas stoves, infrared oven, microwave oven and electric stove are widely used to cook food. Different cooking utensils have their advantages or disadvantages. Depending on the food to be cooked, a desired cooking utensil is selected.
Take an induction cooking stove for example. When a current flows through the induction coil of the induction cooking stove, electromagnetic induction is performed to produce eddy current, thereby heating a foodstuff container. For simultaneously heating multiple foodstuff containers, the heating device needs to have multiple induction coils. By adjusting the electricity quantities to the induction coils, the heating temperatures of respective induction coils are determined.
When multiple induction coils are used to heat foodstuff containers, the induction coils have respective operating frequency values. If the frequency difference between any two induction coils lies within the human hearing range, undesired noise is generated. The user usually feels uncomfortable when hearing the noise. Moreover, since the volume of the noise is varied according to the food type, the food amount, the foodstuff container size and foodstuff container type, the user may mistake a breakdown of the heating device. If the heating device returned to the depot service, unnecessary inspecting cost and time are required.
There is a need of providing an improved heating device so as to obviate the drawbacks encountered from the prior art.